High pressure water cleaning has numerous applications for removing unwanted contaminants and/or surface layers from an object's surface. For example, high pressure water cleaning is used to remove rust from metallic surfaces, paint and accumulated paint from various surfaces, and layers of surface concrete from its underlying aggregate.
Various types of apparatus have been developed for industrial cleaning of parts using high pressure water jets, i.e., where water pressure on the order of 10,000 PSI or more are involved. One important application is the stripping of paint from automobile body dollies so that the paint accumulation does not build up to the point where it may flake off and contaminate the painted surface of the vehicle. Such contamination of the surface is a source of considerable expense and there has been a need in the auto industry to clean the body supporting dollies to avoid such contamination. Heretofore such cleaning has been carried out manually by having workmen armed with a high pressure jet gun manually go over the dollies to strip the paint accumulation therefrom. This, of course, is a labor-intensive operation and therefore the need has arisen to accomplish this automatically.
My experimentation has indicated that while automatic paint stripping using high-pressure water jets appears feasible, being able to control the area of impingement of the jets so that all intended surfaces of the dollies could be stripped proved to be quite difficult. Following considerable experimentation, I discovered that in order for automatic stripping to be carried out satisfactorily certain parameters in the design of the equipment are essential, and as far as I am aware, such have never before been suggested as being necessary for this type of cleaning operation.
In addition, dollies which move continually through the automobile body painting operation may have only been cleaned by taking them out of the system for manual cleaning. This tends to be disruptive of the system and an improved arrangement has been needed for some time.
Conventional apparatus for high pressure water cleaning have included use of a plurality of high pressure water nozzles radially spaced about a common axis for rotation. The nozzles are typically rotated about the common axis to create a circular jet of water. The common axis is moved relative to a surface to be cleaned so that the circular pattern of jet impingement sweeps the surface. If the movement of the common axis (about which the nozzles rotate) is slow enough relative to the surface being swept, the jets will impinge on essentially every portion of such surface and it will be completely cleaned. However, the movement of the common axis would be so slow that the efficiency of the cleaning operation would be unacceptable for use in a production line environment such as the cleaning of automobile body supporting dollies on a body painting line.